Coded track circuit railway signaling system



May 16, 1950 A. L. JEROME CODED TRACK CIRCUIT RAILWAY SIGNALING SYSTEMFiled July 22, 1947 3 Sheets-Sheet 1 W 369 119 A. a.. JEROME CODED TRACKCIRCUIT RAILWAY SIGNLING SYSTEM 5 Sheets-Sheet 2 Filed July 22, 1947INVENTOR. 'Plz l Jr'ozzze.

Ammann/EY 0% *www SYSheets-Sheet 3 INVENTOR.

HIS' WIURNZY A.' L. JEROME .Nwm @www mm CODED TRACK CIRCUIT RAILWAYSIGNALING SYSTEM SNN SNJ

Filed July 22, 1947 May I6, 1950 Patented May 16, 1950 CODED TRACKCIRCUIT RAILWAY SIGNALING SYSTEM Arthur L. Jerome, Edgewood, Pa.,assignor to The Union Switch & Signal Company, Swissvale, Pa., acorporation of Pennsylvania Application July 22, 1947, Serial No.762,617

5 Claims.

My invention relates to coded track circuit railway signaling systemsfor governing the movement of traiiic over stretches of single trackover which trac moves in two directions. More particularly, my inventionrelates to an improved absolute permissive block signaling systememploying cascade-connected reversible coded track circuits, for use ina centralized tralllc control system in which the traffic direction isset up and the head block signals are cleared by manual control from acentral office by means of an intermittently operated communicationsystem, while the intermediate signals, which are controlled solely bythe track circuits, are cleared automatically in one direction or theother in accordance with the direction of energization of the trackcircuit system.

In an absolute permissive block signaling system, such as is hereindisclosed, directional stick relays are provided in connection with theintermediate signals, each of which is normally arranged to becomeenergized when a train passes the associated signal at clear or caution,and when energized prepares a circuit for energizing the next signal inthe rear, governing trailc movements in the same direction to. permitthat signal to indicate caution as soon as the block section in advanceis vacated by a train.

The principal object of my invention is the provision of improved meansfor controlling these directional stick relays bythe track relays of acoded track circuit system, so that each directional stick relay becomesenergized when the code operation of the associated trackrelay-ceasesdue to a train entering the corresponding track section in theestablished direction, but not when the operation of the track relay isdiscontinued due to an opposing train overruning a head block signal norwhen the track circuit system is manually deenergized in preparation forreversing the direction of traffic.

A further object of my invention is to provide improved means of thetype described which is arranged so that the equipment at eachintermediate signal location in the stretch is substantiallyself-contained and does not depend for its operation on special energyimpulses transmitted over the track rails from an adjacent signallocation.

Another object of my invention is to provide improved means of the typedescribed which is arranged so that the operation of the equipment isindependent of changes in operating conditions, such as changes inballast resistance or in the voltage of the batteries from which energyis supplied to the track circuits.

A further object of the invention is to arrange the equipment so thatthe approach relay which governs the lighting of the signal for onedirection of traic also serves to govern the directional stick relay forthe opposite direction of traiiic.

In practicing my invention I employ at each intermediate signal locationmeans operative on release of the code detecting means which governs thesignal to momentarily connect in series across the rails of the tracksection in advance of the signal a source of current and an auxiliaryrelay. This relay has a normally released contact which becomes pickedup only if the energy supplied from the source through the relay windingis of the value which is supplied when the rails of the section areshunted by a train located at or near the entrance end of the section sothat the relay will pick up if release o f the code detecting means wascaused by entrance of a train into the section at that end of thesection but will remain released if release of the code detecting meanswas caused by any other condition. The picking up of this relay governsenergization of the directional stick relay.

The provision of an auxiliary relay and battery, connected to operate asdescribed above, does not comprise my invention per se, but is describedand claimed in an application for Letters Patent of the United States,Serial No. 148,- 967, filed on March 10, 1950, by Crawford E. Staples,for Directional relay control circuits fol railway signaling systems,which application is assigned to the same assignee as the presentapplication.

At double intermediate signal locations the code following approachrelay which governs lighting of the lamp of the signal for one directionof traiiic is employed to govern the directional stick relay associatedwith the signal for the other direction. Where an approach relay isemployed for this purpose its adjustment is controlled so that duringthe period in which the relay is connected across the track rails as aresult of release of a code detecting means, the re.- lay contact willpick up only if there is supplied through the relay winding energy ofthe value which is supplied only if the rails of the associated tracksection are shunted by a train located relatively near the approachrelay.

Other objects of my invention and features of novelty will be apparentfrom the following description taken in connection with the accompanyingdrawings.

I shall describe one form of apparatus embodying my invention and shallthen point out the novel features thereof in claims.

Referring to the accompanying drawings, Figs. 1A, 1B and 1C, placed sideby side in the order listed with Fig. 1A at the left, illustrate thetrack plan and Wayside circuits for a typical single track blockembodying the apparatus of my invention. The block shown includes twosections,

3 over which opposing traic movements are governed by the entering headblock signals ZRA and ERB, Fig. 1A, and by the similar signals 4LA and4LB of Fig. 1C.

Similar reference characters refer to similar parts in each of theseveral views.

Energy for the operation of the relays other than the track relays isfurnished by suitable sources of direct current, not shown, whosepositive and negative terminals are designated B and C, respectively.Each track switch and each railway signal is identied by a numberidentifying its location, the signal designations also including thesuflix L or R to indicate the corresponding direction of trafficmovements to the left or right, respectively. Each relay is identied bya characteristic letter or combination of letters, preiixed by thedesignation of the switch or signal with which it is associated. Thetrack relays ZRTR, GLTR, SRTR, and 4LTR, and also the approach relaysSRAR and SLAR are code following relays of the biased polar type, suchas shown for example in Letters Patent of the United States No.2,057,605, issued October 13, 1936, to Herman G. Blosser. These relaysare constructed and arranged so that the contacts of the relay arenormally biased to their released position and will pick up when andonly when energy flows through the winding in the direction indicated bythe arrow thereon.

The periodically operating contacts of the code following relays aredistinguished from those of the other quick acting relays by horizontaldotted lines indicating their closed positions and the contacts of slowacting relays are identified in the conventional manner by the verticalarrows thereon. It is to be understood that the slow acting relayshaving condensers bridged across their windings have release periods ofabout iive seconds.

Each of the wayside signals shown in the drawings is of the well-knowncolor-light type, having a green lamp G, a yellow lamp Y, and a red lampR, with the exception of signals ZLB and 4RB, which do not include thegreen lamp G. The signals at the ends of the single track section areshown as being continuously lighted, while the intermediate signals 6Land. BRI are arranged to be lighted only when the track section in therear of each signal is occupied by a train.

Inasmuch as my invention relates to wayside apparatus, the centralizedtraiiic control system by means of which the direction of energizationof the signal circuits and the clearing of. the entering signals is madesubject to manual control from a central ofce is not shown herein, butit is to be understood that this is preferably a remote control systemof the code type such as that disclosed in Letters Patent of the UnitedStates No. 2,229,249, issued January 21, 1941.1, to Lloyd V. Lewis, forRemote control systems, or more particularly, as a modification thereofdescribed in a publication entitled Centralized Traic ControlSystem-Time Code Scheme, Manual No. 506A, published by the Union Switchand Signal Company, Swissvale, Pennsylvania. For an understanding of myinvention, it will suiice to point out that the remote control systemhas a eld station at the end of each block which is connected with acontrol ofiice by a line circuit over which codes are transmitted ineither direction for selective communication between the office and thedifferent stations, one at a time. The control codes transmitted to thestations serve to operate a group of control relays of the stick polartype, in accordance with the positions of control levers at the ofice.Two such control relays are shown herein at each station, and thesecomprise a traffic relay such as relay 2RFS, Fig, 1A, which governs thedirection of trafic movements in the single track block by cooperationwith a similar relay 4LFS at the opposite end of the single track block,shown in Fig. 1C, and also include two code signal control relays, suchas the relays ZRHS or LHS, by which the clearing of the correspondinglydesignated entering signals is made subject to manual control from theofi'ice.

Each trac relay LFS or ZRFS when in its normal position as shown, withits left-hand contacts closed, designates its location as the entranceend of its block, in which position the traffic relay enables theadjacent entering head block signal to be cleared under properconditions, in response to the reversal of the associated code signalcontrol relay ZRHS or 4LHS. Each traiic relay when reversed, with itsrighthand contacts closed, designates its location as the exit end ofthe block. In this position the traiiic relay supplies energy to thesignal circuits for the block to enable the signals which govern traicmovements toward its location to be cleared.

The trackway system includes continuous track circuits for all maintrack. The detector sections IT and 3T at the ends of the block eachhave a conventional track circuit including a track relay, such as lTR,which is normally energized by a battery ITB. The remaining trackcircuits ZR-GLT and R/-dLT of the single track block are of thereversible coded type, connected in cascade when the block includes twoor more sections, and provide means for controlling the signals for bothdirections to provide three indications and also for indicating ateither end whether or not the block is occupied, without line wires.

In this application only the portions of the wayside apparatus essentialto the understanding of this invention have been shown and the remainderof the equipment may be arranged in any of several arrangements wellknown in the railway signaling art.

The present invention relates more particularly to the coded trackcircuit apparatus, and is an improvement upon that disclosed in anapplication for Letters Patent of the United States, Serial No. 596,470,filed May 29, 1945, by Henry S. Young for Railway traffic controllingapparatus. In the system of this Young application, the coded trackcircuits are normally deenergized and are set up by manual control byreversing the trafllc relay at the exit end of the block for the desireddirection of traffic movement, and then reversing the code signalcontrol relay for the entering signal at the other end of the block. Thesystem of the Young application is also arranged so that when a trainvacates the block and an indication of that fact has been transmitted tothe office, the operated traine relay is restored automatically tonormal, and the wayside circuits thereby restored to their normaldeenergized condition. This mode of operation may be employed inconnection with the track circuits of my invention. or they may be leftenergized until a reversal of the tralc direction is required to therebyprovide a normally energized system. It is also to be understood thatthe remote control system preferably includes means for preventing the operation of the traffic and signal control relays asovfzw except underthe propertrac conditions, so that a signal cannot be put to stop by theoperation of any lever other than its control lever, one arrangementsuitable for this purpose being disclosed in the above-mentioned Youngapplication.

In the coded track circuit system as disclosed herein, the codedcurrents are generated by code transmitters of the pendulum typedesignated I-80CT andV VECT, which are energized continuously andoperatetheir contacts periodically at a' rate of 180 o1' 75 tiniesper minutes,respectively, to periodically operate a transmitter relay such as relayZRCI, by which the coded energy of. the selectedr frequency is suppliedto the track rails.

Each code following track relay, such as relay ZRTR, is provided with aslow release, .iront contact, repeater, such as the relay ZRTF', whichremains picked up as long as the track` relay is responding to vcodedenergy.

The code responsive apparatus at the Vdifferent signal locations issubstantially similar v and its operation will be understood from adescription of that of Fig. lA, where it will loev seen that the closingof front contact a ofy relay ZRTR in response to the supplyl of animpulse' of coded energy to the winding of relay ERTR establishes thecircuit for supplying energy to the winding of relay ZRTF. When thecontacts of relay ZRTF pick up, its front contact a establishes acircuit for supplying energy to a code following repeater relay ZRTP'each time that' the relay ZRTRY releases its `Contact a. Additionally,when relay ZRTF picks up, its contact b establishes a circuit forsupplying energy to the primary winding of decoding transformerl 2D'I`over' contact a; of relay ZRTP. As the contacts of relay ZRTP arerecurrently picked up and releasedv in response to the code followingoperation of contact a of relay ZRTR, contact a, of relay 2R'I`P`alternately energizes the lower half and the upper half of the primarywinding of decoding transformer ZDT. As a result,V 'current is induced.in the secondary Winding'of transformer 2DT which is rectied by contactb of relay ZRTP and supplied to the winding of a slow :acting codedetector relay ZRH. will be energized when and onlyV whenl they trackrelay ZRTR is following code. Transformer ZDT also supplies codefrequency energy to the' decoding unit lDU which is of a type well knowninthe art. rlhe decoding unit l80DU is constructed and arranged so thatit will supply energy of a value suiiicient to pick up the cont-acts ofArelay ERD when and only when the frequency of the energy supplied tothedecoding unit from transformer ZDT is of the order of 180. cycles perminute. Accordingly, relay ZRD willbe energized. when and only when thecode following Vswitch repeating relay lRWP is energized over vthecontacts N and R of a circuit controller actuated by switch IW. Theserelays serve to select the signal lighting circuits for signals 2BA orZRB, in accordance with the position of' the switch 9W, the selectedsignal displaying a yellow aspect when the code detector relay ZRl-I isenergized, or displaying` a green aspect if relay ZRD is also energized.

It will be seen that the. relay- 2RH` The operation of the system isgenerally similarl for both directions of traffic movement and thecircuits' of Fig; 1C, therefore, are` similar to those of Fig. 1A,except that they are oppositely directed. Likewise, the apparatus at theinter'- mediate signal location of Fig 1B is similar' for each directionbut oppositely directed. In Fig. IB, but one set of decoding apparatusls used, this being arranged for either direction of operation dependingupon which of thetrack relays isoperated, and in addition, a pair ofdirectional. stick relays, such as ERSR,l and BLSR are provided forcontrolling the energization of the track circuit system as required forfollowing train movements inf either direction.

In describing in detail the operation of the system embodying myinvention, itis assumed that the apparatus is in its normallydeenergized condition, as shown. It will now be assumed that theoperator desires to` move a train from right to left through the block.By operation ofthe control levers at the control oiiice, the tralc relayZRFS of Fig. 1A, and the code signal control relay ll'LHS' of Fig. 1Care operated to their reverse positions.

At this time, since signal f'iLA is at stop, the circuit for supplyingenergy to the signal repeater relay ZLAPC* is interrupted and thecontacts of relay ELAPC are released. The circuit for controlling relay2LAPC is not shown, but it may be of any of several` well-known typesinwhich the relay is energized when and only when sig-nal ZLA displays ayellow or a green aspect. Accordingly, a circuit is established tosupply energy of 15 code frequency to the transmitting relay ZRCT. rlhiscircuit is traced from terminal. B', over contact a of code transmitter'F5CT, over back contact a of relay LAPC, iront contact a of relay l-TR,over reverse polar contact a of relay 2RFS and through the winding ofrelay 2RCT to terminal C, whereby the contacts of the relay ZRCT areoperated at the '75 code rate.

When Contact a of relay ZRCT picks up, it interrupts the connection oftrack' relay 2RTR to the rails of section ZR-LT, and establishesv acircuit for supplying energy from the battery 'LPRTBV through thewinding of relay ERTR and the rails ofV section ZR-ELT to the winding ofrelay lLTR, shown in Fig. 1B. This circuit is traced from the positiveterminal of battery ZRTB, over front contact a of relay ZRCT, throughthe winding of relay ZRTR, over rail 5 of section 2Rf--6LT, through thewinding of Yrelay GLTR, Fig. 1B, over back Contact a, of relay GLC-T,and over rail 6' to the negative terminal of battery ZRTB. The directionof'ow of energy is such thatl the contact of relay ZRTR remainsreleased, and the contact of relay SLTR becomes picked up.

When contact a of relay ERCT releases, the circuit traced above isinterrupted, and the contact of relay BLTR. releases. Accordingly, atthis time, the coded energy supplied to the left-hand end of the railsof section ZR-GLT causes the contacts of relay GLTR to be operated atthe 75 code rate. The recurrent operation of the contact of relay BLTRcauses energy to be supplied over front contact a of the relay to thewinding of rel-ay' BLTF, and as a result,the contacts of relay LTF pickup and remain picked up as long as relay ELTR is following code.

When contact ct of' relay GLTF picks up, it establi'shes a circuit forsupplying energy to* the code following repeater relay iTPeach timerelay GLTR releases its contact a'f/' This circuit is ltraced fromterminal B, over back contact 1,- of

relay GLTR, front contact a of relay GLTF, back contact a of relay BRTF,and through the Winding of relay GTP to terminal C. As a result, therelay BTP will recurrently pick up and release its contacts inaccordance with the operation of contact a of relay SLTR.

The primary winding of decoding transformer GDT is now supplied withenergy by a circuit including front contact c of relay SLTF and contacta of relay BTP. The recurrent operation of contact a of relay STP causesenergy to be alternately supplied to the upper and lower portions of theprimary winding of transformer GDT, and as a result, an alternatingcurrent is induced in the secondary winding of the transformer. Thisenergy is rectied mechanically by contact b of relay GTP, and issupplied to the winding of the code detecting relay 6H to thereby causethe contacts of relay 6H to pick up and remain picked u-p as long asrelay ETP is following code. Additionally, energy is supplied from thedecoding transformer GDT to the resonant decoding and rectifying unitISEE DU, but since the code rate at this time is only '75 times perminute, the energy supplied from the decoding unit |80DU to the relay DRis insucient to pic-k up the contacts of relay DR.

When relay 6H picks up, its contact a establishes the circuit forsupplying energy to the code transmitter IBBCT, and contact b of relay6H establishes a circuit for supplying energy to the transmitting relayBRCT, which circuit is traced from terminal B, over contact a of codetransmitter ISSCT, front contact b of relay 6H, over front contact d ofrelay SLTF, over back contact b of relay BRSR, and through the windingof relay BRCT to terminal C. As a result, the contacts of relay SRCT arepicked up and released at the 180 code rate. Additionally, contact c ofrelay 6H establishes the circuit for connecting the condenser Q to thesource and a charge of energy is built up in the condenser.

When the contacts of relay BRCT pick up, a circuit is established tosupply energy from battery SRTB to relay 4LTR, Fig. 1C. This circuit istraced from the positive terminal of battery BRTB, over front contact aof relay GRCT, over front contact b of relay SRCT in multiple with thewinding of relay GRTR, over rail 6 of section 6R-4LT, through thewinding of relay LTR, over back contact a of relay 4LCT, through rail 5of section BR-ISLT, and through the resistor Rl in multiple with thewinding of relay SLAR and resistor R2 to the negative terminal ofbattery SR'IB. A portion of the adjustable resistor R2 is shunted atthis time by the circuit governed by back contact b of relay GRTF, bythe relay GLAR and the resistors Rl and R2 associated therewith areselected and adjusted so that the value of energy which flows throughthe approach relay SLAR at this time is insuiiicient to pick up therelay contact. The direction of ow of energy is such that relay dLTRwill pick up its contact and relay BRTR will remain released. Theshunting of the winding of relay SRTR by front contact b of relay SRCTaffords a lower resistance to the flow of energy in the circuit tracedabove. When the contacts of relay GRCT release, the circuit traced aboveis interrupted, and the contacts of relay 4LTR release. Accordingly, atthis time, the contact of relay 4LTR in Fig. 1C picked up and released180 times per minute in response to the coded energy supplied over therails of section 6R-4LT.

Each time relay 4L'I'R picks up, energy is supplied over front contact ato the winding of relay 4LTF, so that at this time, the contacts ofrelay ALTF are picked up. Each time contact a of relay 4LTR releases,energy is supplied over front contact a of relay 4LTF, to the winding ofrelay 4LTP. Accordingly, the contacts of relay 4L'1P are picked up andreleased 180 times per minute in accordance with the operation ofcontact a of relay 4LTR.

The primary winding of decoding transformer 4DT is now supplied withenergy by a circuit including front contact b of relay ALTF and contacta of relay 4LTP. The recurrent operation of contact a of relay 4LTPcauses energy to be alternately supplied to the upper and lower portionsof the primary winding of decoding transformer 4DT, and as a result, analternating current is induced in the secondary winding of thetransformer having a frequency corresponding to the code rate, which atthis time is 180 per minute. This energy is rectified mechanically bycontact b of relay .LTP and supplied to the winding of code detectorrelay LH to thereby cause the contacts of relay 4LH to pick up andremain picked up as long as relay ALTP is following code. Additionally,energy is supplied from the decoding transformer 4DT to the resonantdecoding and rectifying unit IDU, and since this energy has a frequencyof cylcles per minute, the decoding unit IBBDU supplies sufficientenergy to the relay ALD to pick up its contacts.

Since it is assumed that the code signal control relay ALI-IS has beenreversed by the central office operator and since switch 3W is normal,the picking up of relays LH and ALD establishes a circuit for supplyingenergy to the green lamp of signal GLA. This circuit is traced fromterminal B, over reverse polar contact a of relay 4LHS, over frontcontact b of relay STR, over front contact a of relay 3NWP, over frontcontact a of relay liLH, front contact a of relay 4LD, and through thegreen lamp G of signal 4LA to terminal C. Accordingly, at this timesignal ALA will display a green aspect, indicating proceed If theoperator now clears signal ZLA by means of circuits not shown, the relayZLAPC will become picked up, and its contact a transfers the circuit forsupplying energy to relay `ZRCT from contact a of code transmitter 15CTto contact a of code transmitter IBGCT. As a result, relay 2RCT operatesits contacts 180 times per minute and the supply of energy from batteryZRTB to the rails of section ZR-GLT is coded at that rate.

Relay SLTR, Fig. 1B, now operates its contacts 180 times per minute inresponse to the 180 code supplied to its winding, and repeater relay ETPalso operates its contacts 180 times per minute.

Accordingly, energy of a frequency of 180 cycles per minute is suppliedfrom decoding transformer GDT to the decoding unit IQGDU, which nowsupplies sufcient energy to relay 6D to cause the relay to pick up itscontacts, thereby conditioning the signal 6L to display a proceed orgreen aspect when energy is supplied to its lamps.

The movement of a train from right to left through the single trackblock will now be traced, assuming that the signals 2LA, 6L, and ISLAhave been conditioned to indicate proceed as above described.

When the train moves past signal 4LA and enters the detector section 3T,detector track relay 3TR is shunted and its contacts release. Contact bof relay 3TR interrupts the circuit previously traced for supplyingenergy to the green lamp G of signal ALA and establishes the supply ofenergy to the red lamp R of the signal.

pp'erate its contacts, supplying 'coded energy jfrom 4repeater relay hythe 'eireuit which is traced 'operation ceases. Qontact a of relay 'L'lR're'- leases "and remains released at'tliis time, and 'the *supply Aofenergy to relay'LTF is 'cut oli as a result, but it retains *itscor'actsfpicked'np iintil the energy Lstored in tire4 'eonde'ri'serconnected across its winding is dissipated. The contactsof 'relay vlLTl?are Ipicked up 'continuously iorthis time interval, b'ut 'energy is novlonger lsupplied 'to 'relays lL-I and`LD "fr'om 'the transformer lflDT,:and the contactant these relays release.

Suhseqliently, the Icontacts of relay 'ilLTf felease, interriiptirfg thesnpplyof nefgy'to relay ll'rTP'and to the prirnary Winding oftransformer battery yarma threiehresister RlA and ap through the warrantrear @LAR `and a rortiohef'r'esisto'r Rg jte theraiis efseetidh 3R-'mrDue te the V'shurrtihg erregt of themwheels and Yaxlesuof the train, theCurrent supplied to the rens frem battery 'SRTBYin'creases asthe `train'1513.1 The various parts "o` the 'eqiiipmentarear 'h'gfed andproportion djso 'that distance 'f rthe signal 6L,` as for example feet,the value of currentwhichiiows l'lloll ty'ih'dihg of aphreaehrely thereheeemejsj suffr- Veft toy cause the relay l'to operatemts,contact Eachtime Contact rief 'ielaylLAR pies 'energywis snppli'edto the slow rel seappr h lfrom terminal l, ,overvi'ront c'nta'ctl'c't of relay BLAR, beekeohtaet e 'er relay tarn, het ugh the winding, O f relay .LAltqieimillelf .fSGOdine'ly, relay LAPilgiZS aih... 5111.11?, arid. itsfront Contact q. establishes the circuit for supplying energy y to thegreenlam 4"G of signal Sli, which circuit is tracedromtermlaallaver @et.Ceritact a of relay GEAR frsint'cfmtatifey 6H, over iront Contact d ofrelay GcDyand throughgthe green lamp G of the signal toterrninalg, thnscausing signal 6L todisplay a proceed aspect to the approaching train. Yy

When the rtrain passes. signalllr` and enters section 2R-SLT, relayGL'IKR isshunted audits contact a releases and remains released and4Cuts oi the supplyof energy to relay GLTF. However the relay SLTF issloWYin releasing and after release oi relay BLTR; the circuit 'includingback contact a of relay BLTR for supplying 'energy to relay STP isestablished and the contacts of relay ETP remain picked up for 'asubstantial time interval. The cessation of operation of the contacts ofrelay BTI-cuts off the Supply ofen'ergy from transformer BDT to relays6H and 6D and these relays release after a short 'time interval which isless than the time required for relay BLTF tore'la's'e. When contact dof relay 6H releases the supply of energy to the green lamp Gr of signal8Lj is int'erriipt'ed, andthe circit is established for supplying"energy to the red l'aiiip R of signal 6L. y

The relays GLTF andHRTF are `vselected v.and arranged Withcondensers'nnbs,v of suftliet capaci/ty' so that these relays dwill reniajinpicked "rip r,for i 'comparatively long tn interval 'ftr the restar/rv'VI() rfsin'piy vof fef'rrgy vthereto has been mterupte'd "bythereieese fthe trackreiays.

cA'ieee'rdihgry, 'there will jbe a "'ststantiai itihi'e .intervalbetweenftlieorelea's'eof "relay 'Elia d the q 'release ofrlaiyGL'lFf erthe su'rip'l'yo'f'fe'e'rgy Lreve/aah'or triesejreieyshas been eut'erfIby the "cessation "oi 'operation "of 'the coitact'o "relay "timeihtervalja Leircuitjs esw x p g 'energy from (the vv50ndenser Q 'tejtheft nsriitte'rfrelhly thor. This circuit is 'thacll "fr the-leLE''-llriful4- 'elerrientf coridekr'iser1 Q, over ck Iic'in'tact"'c'of relay Gil-I,- rf htjhhtee't ff for lr y Vtrrrrg -ever back eeh-tact'a or rete-y "thsRfem 'through the wiridingfef relay "GLCT'V'J 'tmifaTCaI'dt thus to the I'glfil-A hand element o f condenser Q.

y "when the'eehtaetsor'reieysLc'rfpiek up'f'er- "f supplied batteryrBLTBv through 'the "er relay BRAB 'over the cireuit which is einthefpostiye 'term-maier batterytLirB, Y ce'rtact a qfreieytnc'r,frhteehtaet Y lay `FaLcT "and the winding 'erreiay SL-TR edted'heult'time,v throughraii 5*, throt'ghthe jelserid asiesef'thetrarhthrmrgh rail '6, arid "thei'i'ceftorftlie atiifeter'rninaVof15attery"6l.TB through the fresis 'r Rfarid Winding "of "relay inserieswhich are'conriected in 'r'nltiple tvitl'i resi'strR'B.

`At thisltime, contact g of l'relay"illi'lis"iicld up, causing 'theentireuai'riounft of 'res''ist'ar'ceI of `Iresistor Rt to 'beinsertedinthe circuit of 'relay there Howeveh with the train khaving iJust"ehteredthe section thefresistace in fthe above "c'ir e ehrhjharatiyelyloma u therelayfRARahd "other portions l 'the 4lcir'cfi't fare selected`so that, 'rretwithstahdihg the 'fact that the whoie or resister Ril isin A'seriestvitli :the Winding o'f'elay SRAR, the current newthroughlthe reia'y'tvihdhg at this time is sff'cie'n'tto 'canse therelay topk its contact. l u l w n When relay picks iipyitswfrontcontacta establi'shres'a circhit 'for sip'plyingenergy tothe "d"ee'tqnalstk relay BLSB. A circuit traded trom terminer B, eterrrehtentect 'eef relay `QGRAR, front ehhtaet e errela'y fsLTF, andVtlir'fjvfglri the winding 'of relay BLSR to Aterminal C. When thee htaetsjefjreiaysLsRi-'pekuefa V'stick"circriiit is established tomaintain the "relay enea 'energized and 'is traced frein terrain@ B,over back contacte yof Arelay 6I-I, 'over front oontaet bf reiay'tLsrt,'hd through the wind'iig of rei'a'ytnsa te terminare. nAdditien'aliyhwhen relay' sL'sR picks "up, its "onta'trt interrupts the'circuit p'rv'osly 'traced :for Spplying Penergy'to 'thewinding of relayBLCT, and `its 'contacts 'release and "interrupt the-hup ply of energyfrehrhattery GILTB torelay 'aRAR'se that relay BRAB 'releasesandihterrupt's thepiea dp 'circitef relay SILSR. LThe relay SLOT isihadeslightly slow in'releasing by. means of 4a 'snubbing resistorYconnected'across the winding 'ofA relay ELCT 'and after the lsupplyofenergy to 'the :Winding ofrelay SL'CT is interrupted', its contactsremain picked 'up fora short time interval', thus 'assuring 'thatrelay/SRARwill remain pickedup "andw'n'aintain the siipp'l'y of "energyto r'elay'lLSR for asufci'ently lngtirne interval to insure 'that"Contact b 'f relayBLSR establishes'tle stick c'i'r- 'cit traced above.

A short timeiater, relayLTF releases' and its "Contact b 'additionallyinterrpts the. pickup circuit tvhi'ch 'ii/afs previously. traced forrelay BLSR. Al'so'contact i7 frelay GLTF again shunts part of theresistor R4 in series with the .Winding '15 of 'relay lSRAR, 'bt at thistimerelay 'SLCTi re,-

leased and the circuit of relay GLCI is interrupted by contact a ofrelay BLSR with the result that relay BLCT will remain released so thatrelay GRAR will not pick up again.

When contact f of relay BLTF releases, a circuit is established fordischarging any energy remaining in the condenser Q at this time. Thiscircuit is traced from the left-hand element of condenser Q, over backcontact c of relay 6H, back contact f of relay BLTF, and over backcontact f of relay SRTF to terminal C and thus to the right-hand elementof condenser Q.

At this time the code transmitter 'I5CT is set into operation by thesupply of energy thereto by a circuit including front contact c of relayGLSR.

When contact b of relay 6H releases due to the entrance of the traininto section 2R-6LT, the circuit previously traced for supplying energycoded at 180 times per minute to the transmitter relay SRCT isinterrupted. Shortly thereafter, relay BLSR picks up and its frontcontact d establishes a circuit for supplying energy coded at 75 timesper minute to the transmitting relay BRCT. This circuit is traced fromterminal B, over contact a of code transmitter CT, front contact d ofrelay SLSR, over back contact b of relay GRSR, and through the Windingof relay GRCT to terminal C.

As a result, energy is now supplied to the rails of section BRf-ALT atthe 75 code rate, and since the rear portion of the train still occupiessection BRf-IELT, the approach relay GLAR will now operate its contactsat the 75 code rate, and relay GLAP will remain energized. The releasetime of relay BLAP is made sufficiently long to bridge the timenecessary for the equipment to operate to change the code speed of relayBRCT from 180 to 75 times per minute.

When the train under discussion vacates section BR-IILT, the removal ofthe shunt decreases the amount of current supplied thereto from thebattery ERTB, and as a result, the flow of energy through the winding ofrelay BLAR falls below the value necessary to pick up the contact ofrelay GLAR and it remains released. Accordingly, energy is no longersupplied to relay BLAP over the circuit including front contact a ofrelay GLAR, and after a time interval, the contact of relay ELAPreleases.

When contact a of relay BLAP releases, it interrupts the circuitpreviously traced for supplying energy to the lamps of signal 6L, and,as a result, the red lamp R of signal 6L is extinguished.

1 At this time, as previously explained, energy coded 75 times perminute is supplied to the rails of section 6Rf-4LT by the operation ofthe contacts of transmitting relay GRCT, and when the section is vacatedrelay IILTR responds to the '75 code supplied over the rails of section6R-4LT, energizing relays 4LTF and 4LH in a manner similar to thatpreviously described. However, since the contacts of relay 4LTP areoperating at the '75 code rate, the relay ALD does not receive suicientenergy from decoding transformer 4DT and the decoding unit I80DU to pickup its contacts at this time. Consequently, if relay 4LHS is againreversed by the operator, signal ALA will be cleared in a manner similarto that previously described, except that, since relay 4LD is released,the signal will display a yellow aspect, indicating that the next signalis displaying, or is conditioned to display, a red aspect.

As the train passes signal 2LA, and enters the l2 detector track sectionIT, the detector track relay ITR is shunted and its contacts release.

When contact a of relay ITR releases, the circuit previously traced forsupplying energy to transmitting relay 2RCT is interrupted so that codedenergy is not supplied to the rails of section ZR-'GLT after the trainvacates that section. Additionally, it is to be understood that when thetrain under consideration enters section IT, signal 2LA will be put tostop, and as a result, the relay 2LAPC will be deenergized and itscontact will release.

When the train vacates section IT, relay ITR picks up, and contact a ofrelay ITRI again establishes the circuit for supplying energy to relay2RCT. However, since the relay ZLAPC is released at this time, thecircuit is governed by contact a of code transmitter 15CT, so that relay2RCT supplies energy coded at the '75 code rate from battery ZRTB to therails of section ZR-SLT.

The relay BLTR follows the coded energy supplied thereto over the rails0f section ZRf-GLT, and as a result, the relays GLTF and 6H pick up, aspreviously described. When contact a of relay 6H picks up, it interruptsthe stick circuit previously traced for relay SLSR, and relay ELSRreleases. When relay GLSR releases, its front contact d interrupts thecircuit previously traced for supplying energy to the relay GRCT overcontact a of code transmitter 15CT, and additionally, contact c of relaySLSR interrupts the supply of energy to the code transmitter 15CT.

The code transmitter IBUCT is now energized by the circuit includingfront contact a of relay 6H, and front contact b of relay 6H and frontcontact d of relay BLTF again establish the circuit for controllingrelay BRCT over contact a of code transmitter I8UCT. Also, the condenserQ is supplied with energy over front contact c of relay 6H. Frontcontact d of relay 6H, and back contact a of relay 6D prepare thecircuit for supplying energy to the yellow lamp of signal 6L should anapproaching train cause the relay GLAP to pick up, as previouslydescribed.

With the contacts of relay BRCT operating at the code rate, energy issupplied from battery GRTB to the rails of section SR-IILT at the rateof 180 impulses per minute. The response of relay 4LTR. to the codedenergy supplied thereto causes the relays 4LTF, 4LH, and 4LD to pick up,as previously explained. Energization of relay 4LD may be employed inany suitable manner to indicate that the entire single track stretch isvacant, but this means is not part of this invention and has beenomitted in order to simplify this disclosure.

With the single track block unoccupied, and the traiic relay 2RFSreversed to set up the direction of movement from right to left, asdescribed above, it is assumed that the operator at the control oicerestores the traftlc relay ZRFS to normal.

When reverse contact a of relay ZRFS opens, the supply of energy torelay 2RCT is cut off. As a result, energy is no longer supplied frombattery 2RTB over the rails of section ZR-SLT to relay SLTR, and relayBLTR releases and remains released.

As previously explained, the release of contact a of relay GLTR resultsin the release shortly thereafter of the contacts of relay BH, but thecontacts of relay SLTF remain picked up for a, frelatively long timeinterval after release Vof relay GLTR..

When contact c of relay 6H releases, it establishes the previouslytraced circuit for supplying energy from condenser Q to the winding ofrelay GLCT. Accordingly, the contacts of relay 6LCT pick up and connectthe battery fLTB across the rails of section ZR-BLT in series with theresistor R4 and the Winding of relay GRAB. in parallel with resistor R3.

At this time, contact g of relay BLTF is picked up, and the entireresistance of resistor Put is connected in series with the Winding ofrelay BEAR, but since section ZR-GLT is assumed to be unoccupied, thevalue of energy which ilows through the winding of relay GRARis-insufcient to pick up the contacts of the relay. As va result, thecircuit previously traced for picking up the directional stick relay@LSR is not established by vfront contact a of relay GRAR, and relayBLSR does not pick up at this time.

After a short time interval, the energy from condenser Q is dissipated,and relay BLCT releases, cutting of the supply of energy from batterySLTB to the rails of section 2R--6LT.

When relay SLTF releases, its front contact f interrupts the circuitrfor supplying energy to relay yGLCT from condenser Q, and if relay BLCTis not released, itreleases at that time.

`When relay 6H released its contacts, its front contact .a interruptedthe supply of energy to code transmitter 'l3CT, and front contact b ofrelay 6H interrupted the circuitl for supplying energy to relay @RCTover contact a of code transmitter lCT, and since relay SLSR does notpick up at this time to supply energy over its front contact d andcontact a of code transmitter 'ISCT to the winding of relay BRCT, thecontacts of relay SRCT remain released.

As a result, coded energy is no longer` supplied from battery @RTB overthe rails of section 6R-4LT to the winding of relay 4LTR, and relay lLTRreleases, which results in the releasing of relays 4LTF, 4LTP, @LH andALD, as previously explained.

The system is now vrestored to its normal lor deenergized condition asshown in the drawings.

The energy impulse supplied to the rails of section ZR-GLT during thepicked up period of relay SLCT will pick up track relay ZRTR at theother end of the section, and relay ZRTF will pick up as a result. Whencontact b of relay 2RTF picks up it establishes the circuit forsupplying energy to the primary Winding of transformer ZDT with theresult that a pulse of energy of small value is induced in thetransformer secondary winding and is supplied therefrom to relay ZRH.When relay ELCT releases, and the supply of energy to relay ZRTR is cutoff, the circuit previously traced for energizing relay 2RTP isestablished, and relay ZRTP picks up, thereby causing a pulse of energyof normal value to be supplied through transformer ZDT to relay ZRH.After a comparatively long time interval, relay 2RTF releases, therebyinterrupting the supply of energy to the primary winding of transformer2DT and causing the release of relay ZRTP. At this time a pulse ofenergy of small value is supplied through transformer 2DT to relay ZRH.These pulses, however, are of such value and are separated by such timeintervals as to be ineiective to pick up relay ERI-I. Accordingly, theoperation of the apparatus when returning to the deenergized state issuch that false operation of the'controlled signals cannot result.

v.Frz'n'm the foregoing it will be seen that `the ii-- rectional stickrelay, such 'as relays BLSR or GRSR, lis energized when the codeoperation of the associated track relay ceases as a result of ,a

train entering the corresponding track sectionat the entrance endthereof, but is not energized if the code operation of the track V.relayceases when the section is not occupied.

This result is secured by vproviding at each intermediate signallocation means effective upon release of the code detecting relaygoverned by Aa track relay at that location vto temporarily .connect theassociated track battery and approach relay in series across the railsof the track section in advance of the signal. At this time the approachrelay is adjusted so that energy sufcient to pick up the relay contactissupplied from the track battery through the winding of the approachrelay only if a train is present at that end of the track section, Whilethe directional stick relay is governed by the approach relay so as tobe picked up if the approach relay picks up at this time.

When the track battery is connected across the track rails at an end ofa track section in series With the Winding of the approach relay theenergy supplied through the winding of the approach relay is of a highvalue if a'train occupies that end of the track section but is of a lowvalue if the track section is not occupied, or if a ,train is present ina distant portion of the track section so that a considerable length of.track rail is included inthe circuit :of the `track battery andapproach relay.

Occupancy kof an end portion of a track section produces a much greaterincrease in the value of the energy supplied from the track batterythrough the winding of the approach relaythan is produced by variationsiin other conditions, such as changes in lballast resistance or in thevoltage of the track battery. Accordingly, at the time the codedetecting relay releases the approach relay may be adjusted to respondonly to energy of relatively high value so that if that end of the tracksection is not occupied, the approach relay will not respond to energyof the value supplied as a result of high battery voltage or low ballastresistance, or vas .a result of both conditions, but so that Atheapproach relay will be certain to respond if that end of the tracksection is occupied.

As a result this method of controlling the directional stick relayinsures that the relay will be picked up to cause coded energy to besupplied to the track stretch behind a train when release of a codedetecting relay is caused by occupancy of a track section, and at thesame time it 1insures that Variations in operating conditions will notcause a directional stick relay to be improperly picked up when releaseof a code detecting .relay occurs because the supply of coded energyover the rails of a track section is cut off for the purpose ofdeenergizing the track circuit apparatus.

Myinvention is advantageous in that no control pulse need be transmittedfrom the locations at each endof the single track block to anintermediate signal location, ,or from one intermediate signal locationto another, to cause the system to assume its deenergized condition. Ifthe supply of coded energy from battery ZRTB, for example, isinterrupted during a time when the-system is set up fortrafc to movefromright to left, if no train is occupying the section ZR-AELT, theequipment at the intermediate vsig- 15 nal location BL--GR will assumeits deenergized condition, as previously explained, and Will cut off thesupply of coded energy to section 6R-4LT, to thereby cause the releaseof the relays 4LH and 4LD at the other end of the single track block.

An additional advantage which is gained from this arrangement is that itcauses all of the opposing signals governing traffic in the single trackblock to assume the stop position in case a train overruns the enteringhead block signal at the exit end of the block. If a train moving fromleft to right should pass signal 2BA at a time when signals 6L and dLAare cleared for a train movement from right to left, the entrance of theoverrunning train into detector section IT will cause relay ITR torelease with the result that its front contact a interrupts the circuitfor relay ZRCT. Accordingly, the supply of coded energy to sectionZR-GLT is cut off, and as previously explained, the equipment at signal6L and also at signal ALA is restored to its deenergized condition Withthe result that the signals indicate stop,

The equipment operates in a manner similar to that described in theforegoing when the single track block is conditioned for traflicmovements from left to right, when a train moves through the stretchfrom left to right, and when the system is being deenergized, and adetailed description of the operation of theequipment is deemedunnecessary.

It is to be understood that although only one set of intermediatesignals, GL and 6R, are shown in the drawings, the invention is notlimited to this arrangement and any number of intermediate signals maybe provided as necessary. Additionally, the conventional cut sectionsand hand-operated track switches equipped with electric locks may beinterposed as desired without affecting the operation of the arrangementof equipment embodying my invention.

Although I have herein shown and described only one form of coded trackcircuit signaling system embodying my invention, it is to be understoodthat various changes and modifications may be made therein within thescope of the appended claims without departing from the spirit and scopeof my invention.

Having thus described my invention, what I claim is:

1. In a coded track circuit signaling system, in combination, a stretchof railway comprising adjoining rst and second track sections, means forat times supplying coded energy to the rails of said first section atthe end thereof remote from said second section.v a code following trackrelay connected across tlie rails of said first track section at the endthereof nearest said second section, a slow release relay energized as aresult of operation of said track relay, means operative upon release ofsaid slow release relay for momentarily connecting a battery and thewinding of an auxiliary relay in series across the rails of said rsttrack section at the end thereof nearest said second track section, saidauxiliary relay having a normally released contact which becomes pickedup or remains released cording as the energy supplied through theWinding of said auxiliary relay is of the value which is supplied whenthe portion of said first track section nearest said second tracksection is occupied or is of the value which is supplied when theportion of said rst track section nearest said second track section isvacant, a directional relay having contacts movable between a nor-f maland an operated position, means responsive to picking up of the contactof said auxiliary relay for moving the contacts of said directionalrelay to their operated position, means responsive to picking up of thecontacts of said slow release relay for moving the contacts of saiddirectional relay to their normal position, and means effective when thecontacts of said directional relay are in their operated position or thecontacts of said slow release relay are picked up for supplying codedenergy to the rails of said second track section.

2. In a coded track circuit signaling system, in combination, a stretchof railway comprising adjoining rst and second track sections, means forat times supplying coded energy to the rails of said rst section at theend thereof remote from said second section, a code following trackrelay connected across the rails of said rst track section at the endthereof nearest said second section, a slow release relay energized as aresult of operation of said track relay, means operative upon release ofsaid slow release relay for momentarily connecting a battery and thewinding of an auxiliary relay in series across the rails oi said rsttrack section at the end thereof nearest said second track section, saidauxiliary relay having a normally released contact which becomes pickedup or remains released according as the energy supplied through thewinding of said auxiliary relay is of the value which is supplied whenthe portion of said first track section nearest said second tracksection is occupied or is of the value which is supplied when the por,tion of said first track section is vacant, a directional stick relayhaving normally released contacts, a pick-up circuit for saiddirectional stick relay established when the contact of said auxiliaryrelay picked up, a stick circuit for said directional stick relayincluding a front contact of said directional stick relay andinterrupted when said slow release relay picks up, and means effectivewhen the contacts of said directional relay are picked up or thecontacts of said slow release relay are picked up for supplying codedenergy to the rails of said second track section.

3. In a coded track circuit signaling system for a stretch of singletrack railway comprising adjoining rst and second track sections, saidfirst track section having at the end thereof nearest said second tracksection a transmitting relay having contacts which normally occupy a rstposition and are movable therefrom to a second position, saidtransmitting relay contacts being operative ywhen in their rst positionto eifectively connect the winding of a code following track relayacross the rails of said first track section and being operative when intheir second position to connect a track battery and the winding of acode following approach relay in series across the rails of said firsttrack section, said signaling system including a signal governingentrance of traffic into said second track section from said rst tracksection and having means governed by traffic conditions in said secondtrack section for governing said signal and for at times operating thecontacts of said transmitting relay between their two positions, saidsignaling system also including means for at times supplying codedenergy to the rails of said rst track section at the end thereof remotefrom said second track section, a iirst and a second slow release relaywhich are picked up in response to operation of said track relay, saidsecond slow release relay remaining picked up for a time intervalsubsequent to release of said first slow release relay on cessation ofoperation of said track relay, means effective when the contacts of saidfirst slow release relay are picked up for supplying coded energy to therails of said second track section at the end thereof nearest said firsttrack section, an approach repeater relay effective when energized toestablish a circuit for a lamp of said signal, and a directional stickrelay effective when picked up to cause coded energy to be supplied tothe rails of said second track section at the end thereof nearest saidrst track section while said first slow release relay is released, thecombina tion with the foregoing apparatus of im-proved means forgoverning said approach repeater and directional stick relays by saidcode following approach relay, said means comprising means effectiveaccording as said second slow release relay is released or is picked upto condition said code following approach relay to pick up in responseto energy of the value which is supplied through the relay winding whena train is present in said rst track section within a substantialdistance of the end of said track section nearest said second tracksection or to pick up only in response to energy of the value which issupplied through the relay winding when a train is present in said rsttrack section within a relatively short distance of the end of saidtrack section nearest said second track section, a circuit including afront contact of said code following approach relay for supplying energyto said approach repeater relay, and means responsive to picking up ofthe contact of said code following approach relay while said second slowrelease relay is picked up for supplying energy to said directionalstick relay.

4. In a coded track circuit signaling system for a stretch of singletrack divided into track sections, said signaling system comprising codetransmitting means and a code following track relay associated with eachend of each of said track sections, decoding means responsive to thecoding operation of each track relay except those for the extreme endsof the stretch for governing the operation of the code transmittingmeans for the adjacent end of the adjoining track section, manuallycontrolled means for each end of said stretch for rendering theassociated code transmitting means active and thereby cause transmissionof code pulses over the track rails of the successive track sectionstoward the opposite end of the stretch for preparing the stretch for onedirection of train movement, and a directional stick relay associatedwith each of said track relays except those for the extreme ends of thestretch and effective when energized to cause operation of the codetransmitting .means for the adjacent end of the adjoining track section,the combination with the foregoing apparatus of improved means forpicking up said directional stick relays when and only when release ofthe associated decoding means is caused by entrance into thecorresponding section of a train moving in the established trainodirection, said means comprising means effective upon release of thecode detecting means at an end of a section to momentarily connect inseries across the rails of the associated section at that end of thesection a source of current and the winding of an auxiliary relay havinga contact which remains released or becomes picked up according as theenergy supplied from said source through said auxiliary relay winding isof the value which is supplied when the portion of said track section atthat end of the section is vacant or is of the value Iwhich is suppliedwhen the portion of said track section at that end of the section isoccupied, and means responsive to picking up of one of said auxiliaryrelays for supplying energy to the associated directional stick relay.

5. In a coded track circuit signaling system for single track railroads,a stretch of single track divided into a plurality 0f track sectionswith a head block signal at each end for governing tralc in oppositedirections into said stretch and with intermediate signals located atintervals in the stretch, code transmitting means and a code followingtrack relay associated with each end of each of said track sections,decoding means responsive to the coding operation of each track relayfor governing the indication of the associated signal, each of saiddecoding means except; those at the extreme ends of the stretch beingeffective when energized to cause operation of the code transmittingmeans for the adjacent end of the adjoining track section, manuallycontrolled means for each end of the stretch for rendering theassociated code transmitting means active and thereby cause transmissionof code pulses over the track rails of the successive track sectionstoward the opposite end of the stretch for preparing the stretch for onedirection of train movement, each of said intermediate signals havingassociated therewith a code following approach relay responsive to theKcode pulses which are supplied to the adjacent end of the adjoiningtrack section, each of said approach relays having a normally releasedcontact which becomes picked up when the code pulses supplied to theassociated track section are of the value which are supplied when atrain advances in said section within a relatively long distance of saidapproach relay, each of said approach relays being effective when itscontact is operated to energize a slow release repeater relay which whenenergized establishes a circuit for a lamp of the signal with which theapproach relay is associated, each of said intermediate signals alsohaving associated therewith a normally released directional stick relayeffective when energized to cause operation of the code transmittingmeans for the adjacent end of the adjoining track section, thecombination with the foregoing apparatus of improved means forcontrolling the pick-up circuits for said directional stick relays, eachof said means comprising means effective on release of the decodingmeans governing an intermediate signal to momentarily connect across therails of the section with which the decoding means is associated thecode following approach relay associated with that end of said sectionand during this period rendering said code following approach relayresponsive only to energy of the value which is supplied through therelay winding when the portion of said section within a relatively shortdistance of said code following approach relay is occupied by a train.

ARTHUR L. JEROME.

REFERENCES CITED UNITED STATES PATENTS Name Date Van Horn Mar. 21, 1944Number

